I recently added this site to my list after seeing the video of the construction process. Do go there and have a look.

The author’s use of fired clay is impressive enough but the heated floor is what really caught my attention. It works the same way as the Roman hypocaust and Korean ondol. I was some way though viewing that portion of the build before it dawned on me what I was looking at.

The Roman designs heated large surface areas and large masses of masonry, leading to the need for a lot of labor to feed the furnace. Although this was probably not a big deal from the Roman point of view because of the prodigious use of slaves. But the author’s use of large stones in the floor covering a heating channel should provide a source of radiant warmth for the entire living space long after the fire went out. And would require less labor for the resultant heat.